Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

Figure 7.24. 
The role of 
inversion processes in 
limiting the dispersion 
of air pollution formed 
in urban territories 
There are the following 
features characterising 
the photochemical smog:
1.  it is formed in a clear, 
sunny weather at a low 
air humidity;
2.  chemically the smog 
atmosphere acts as an 
oxidizing agent; 
3.  it causes the irritation 
of mucous membrane 
and the upper respi‑
ratory tract, adversely 
affects plants and 
animals;
4.  it is seen as a bluish 
haze or mist.

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7. AIR POLLUTION
 149
hydrocarbons emitted with the exhaust of vehicles are the source of 
a vast range of organic substances. Under the smog conditions free 
radicals, phenols, peroxides, aldehydes, ketones, carboxylic acids 
and other substances are formed from hydrocarbons, which largely 
determine  the  biological  effect  of  the  photochemical  smog.  The 
free radicals are capable of reacting with nitrogen oxides, forming 
nitrates  and  with  ozone  forming  peroxides  and  ozonides  –  the 
substances whose physiological activity is particularly high.
0
4
8
12
16
20
24
NO
NO
2
Hydrocarbons
O
3
Concentration
Daynight, h
First of all, the harmful effect of ozone must be noted, which 
is determined by the fact that ozone is a powerful oxidizer. Thus, it 
causes irritation, can trigger asthma and affect lung function. The 
maximum  permissible  concentration  level  of  ozone  set  in  USA  is 
0.1 cm
3
/m
3
. Ozone is able to accelerate the deterioration processes 
of  polymer  materials  and  rubber.  The  negative  effect  of  increased 
ozone concentration on plants has also been proven, for example, in 
California it inflicts a real material damage.
Another group of substances with the most evident physiological 
effect  are  peroxides  and  nitrites,  especially  peroxyacetyl  nitrates. 
These substances are characterized by high toxicity and irritant 
effect (they cause eye watering).
In contrast to the photochemical smog, the London-type smog 
is formed in humid air, especially if there is a limited dispersion of 
pollutants (inversion conditions) and, above all, it is determined by 
sulfur dioxide, carbon monoxide and aerosol influence. Entering into 
the humid air atmo sphere, sulfur dioxide dissolves in fog droplets 
creating inhalable aerosols, which, unlike sulfur dioxide, are not 
absorbed in the upper respiratory tract and mucous membranes of 
the nose, but enter the lungs.
In alveoli the sulfur dioxide sorbed in aerosol particles is 
desorbed, causing irritation that can lead to impaired lung function, 
Air pollution in 
photo chemical  smog 
conditions may adversely 
affect:
1.  human well‑being and 
health;
2.  materials and 
products;
3.  plants and animals;
4.  atmospheric composi‑
tion and the processes 
therein.